Objectives:
1. By titrating with an acid and an alkaline solution, students will
understand that an acid added to an alkaline can become
neutralized and by adding more acid, the alkaline solution can
become acid.
2. After demonstrating the titration of an acid and an alkaline
solution, students will perceive that the pH factor, a measure of
acidity, neutrality, or alkalinity of a liquid or a solid in
relation to their own bodies.
3. Students will gain an understanding of the titration experiment by
using the abstract pH factor color charts and transferring the
positions to signed numbers (positive or negative numbers).
4. By using the abstract tube for their number lines, students will
become aware of the importance of the number line and usage of
signed numbers.
Apparatus Needed:
Two 500 ml beakers
Four 200 ml flasks
Four eyedroppers
1M of NaOH (Sodium Hydroxide)
1M of HCl (Hydrochloric acid)
One bottle of litmus paper (blue)
One bottle of litmus paper (red)
One bottle of antacid
One box of baking soda
One bottle of wide range pH 3.0 to 11.0 of phenolphthalein
Six 17cm x 21cm of acrylic glass, colors--red, orange, yellow,
green, clear, and blue.
One long tube about 270 centimeters long and 6 3/4 inch in diameter
Two red plastic book covers and two blue plastic covers
Recommended Strategy:
Be prepared to encourage students to see how the phenolphthalein has
the property of turning blue in NaOH (Sodium Hydroxide) and turning
red in HCl (Hydrocloric acid), and adding HCl drop by drop with
stirring to the sodium Hydroxide will become colorless. An alkali
neutralizes of an acid to water and salt solution.
1. Pour 1M of NaOH into a 500 ml beaker, and pour 1M of HCl into a 500
ml beaker. Pour from the 500 ml beaker of NaOH into a 200 ml flask
about 100 ml, and two or three drops of the phenolphthalein into
the 200 ml flask of NaOH.
2. Repeat the same for HCl.
3. Take out a blue litmus paper, drop a little of HCl from the 200 ml
flask. The red color shows that hydrochloric acid is an acid.
Take out a red litmus paper. Drop a little of NaOH from the 200 ml
flask. The blue color shows that sodium hydroxide is an alkali.
4. Have the students to take a blue litmus paper and a red litmus
paper, placed under their tongue. If the red color shows from the
blue litmus paper of a pale pink color, they are somewhat acidity.
if the blue color shows from the red litmus paper of a pale blue
color, they are somewhat alkali.
5. Add HCl (hydrochloric acid) from the 200 ml flask where the drops
of phenolphthalein was added to the solution, drop by drop with
stirring to the 200 ml flask of sodium hydroxide where the few
drops of phenolphthalein was added to the solution. When the
sodium hydroxide becomes colorless, the reaction has neutralized.
When the sodium hydroxide becomes red, the reaction is completed.
6. Pour NaOH (sodium hydroxide) from the 500 ml into another flask.
Add two or three drops of phenolphthalein. Add sodium hydroxide
from the flask drop by drop with stirring to the hydrochloric
solution from the 200 ml flask. When the hydrochloric acid becomes
colorless, the reaction has become neutralized. When the
hydrochloric acid becomes blue, the reaction is completed.
7. Pour HCl from the 500 ml beaker into another flask. Add two or
three drops of phenolphthalein. Add two - four teaspoons of an
antacid that have aluminum hydroxide and magnesium hydroxide, both
are alkali solutions, to the HCl in the flask. The hydrochloric
acid becomes white, the reaction has become neutralized.
8. Pour HCl from the 500 ml beaker into another flask. Add two or
three drops of phenolphthalein. Add l/2 teaspoon of baking soda
(sodium bicarbonate), a source of alkali, to the HCl in the flask.
The hydrochloric acid or HCl becomes a clear lime color.
9. Divorce chemistry and explain to students that the concentration of
hydrogen ions in a water solution is normally a matter of
importance for the hydrogen ion is responsible for all acid
properties and that includes us. The concentration of hydroxide
ions will be basic or alkali. In mathematical form it is pH = log
1/(H+) and pOH = log 1/(OH-). The pH is the logarithm of the
reciprocal of the molar concentration of the hydrogen ion and the
pOH is the hydroxide ion.
10. Take the two red plastic book covers and measure the amount needed
to put inside the tube (about 6 1/4 inches wide) glue the edges
with acrylic glue.
ll. Take the two blue covers and repeat the above.
12. Cut acrylic glass 17.5 x 21cm of red, orange, yellow, green, clear,
and blue for a pH chart.
13. Demonstrate how to use the mathemathical approach for signed
numbers using the tube. Let red represent positive numbers and
blue represent negative numbers.
l4. Place chart on chalkboard--magnetic strips can be used to hold
acrylic chart. Students can select a color from the pH range to
represent the continuum of signed numbers.
If more information is needed on the use of " Vision Props" of signed
numbers, this author can be reached after 6:00 P.M.